It's preference, I'd say try a couple of matches on a few sensitivities. Honestly I like 5 your able to do a lot more and still be consistent with all weapons.

what ever you like

I played on 5 back when i used to play

I play on 2-4.

Time to end this. The two best players in the game are Roy n Pistola, they use 3, and 5 sens. Pick one /thread

^ that

3 or 4.
It depends.. usually if i play a lot i play 4.. but after a big break or just casual playing it's 3.